In the technique for circulation and compression of gas, in particular air, the use of starting valves which facilitate starting of the compressors or blowers in the presence of a backpressure at the system outlet is fairly common.
The presence of said backpressure generates a load on the compressor even with the machine at a standstill, consequently determining a sudden high electricity requirement and therefore an overload at starting of the operating machine such as to prevent the operation thereof due to the high current absorption of the electric starting motor.
Currently starting valves exist on the market which permit no-load operation for a temporary period, thus allowing operation of the compressors and blowers to be correctly controlled, avoiding undesired overloads.
The appropriate starting valve is chosen according to the system operating pressure and the volume of gas to be treated.
The presence of such a starting valve allows elimination of the starting overload, equalising the pressure between the compressor inlet and outlet, thus eliminating the pressure difference which would otherwise generate the high initial overload.
Immediately after, the starting valve progressively closes until it reaches the valve calibration value, which corresponds to the operating pressure of the entire system.
The gradual closing of the starting valve allows a progressive load to be generated on the operating machine and therefore on the operating machine electric starting motor.
However, the starting valves currently present on the market do not allow a degree of precision in pressure adjustment such that they may be successfully applied in both pressure and vacuum applications.
Therefore, the aim of the present invention is to conceive a starting valve which has a high pressure adjustment precision also in systems with fluid operating machines working in a vacuum.
For production of the present starting valve, the already consolidated construction criteria of simplicity and inexpensiveness of the well-known pressure applications have been used.
The present starting valve is particularly useful in all vacuum applications with a low expansion ratio (i.e. a ratio between the atmospheric pressure and the absolute operating pressure of the system no higher than 5) with high gas flow rates.
The present starting valve, in addition to facilitating starting of the operating machines, has the function of guaranteeing the maintenance of a constant working pressure (±1% of the required pressure), a factor which has proved to be fundamental for correct efficient operation in these types of applications.